Table Of Contents

Layer 2 Tunnel Protocol (L2TP)

Technology Description

L2TP

Inventory and Information Model Objects (IMOs)

Layer 2 Tunnel Protocol Interface

Layer 2 Tunnel Protocol Session Entry

Vendor-Specific Inventory and Information Model Objects

Redback's Layer 2 Tunnel Protocol Peer

Redback's Layer 2 Tunnel Protocol Group

Redback's Layer 2 Tunnel Protocol Domain Entry

Network Topology

Service Alarms

Layer 2 Tunnel Protocol (L2TP)

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This chapter describes the level of support that Cisco ANA provides for L2TP, as follows:

•Technology Description

•Inventory and Information Model Objects (IMOs)

•Vendor-Specific Inventory and Information Model Objects

•Network Topology

•Service Alarms

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Note L2TP technology for Cisco devices is currently not supported.

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Technology Description

L2TP

L2TP acts like a Data Link layer (Layer 2) protocol for tunneling network traffic between two peers over an existing network (usually the Internet). The two endpoints of an L2TP tunnel are the initiator of the tunnel, the L2TP Access Concentrator (LAC), and the L2TP Network Server (LNS), which waits for new tunnels. Once a tunnel is established, the network traffic between the peers is bidirectional.

L2TP is in fact a Session Layer (Layer 5) protocol, as the entire L2TP packet is sent within a UDP datagram, while it is common to carry Point-to-Point Protocol (PPP) sessions within an L2TP tunnel. L2TP does not by itself provide confidentiality or strong authentication. IPsec is often used to secure L2TP packets by providing confidentiality, authentication and integrity.

Inventory and Information Model Objects (IMOs)

This section describes the following IMOs:

•Layer 2 Tunnel Protocol Interface (IL2TPTunnel)

•Layer 2 Tunnel Protocol Session Entry (IL2TPSessionEntry)

Layer 2 Tunnel Protocol Interface

The following Layer 2 Tunnel Protocol Interface object represents one edge of an L2TP Tunnel. It aggregates multiple Layer 2 Tunnel Protocol Session Entries, which it is bound to by its Session Table attributes, while being aggregated by a Layer 2 Tunnel Protocol Peer, from which it is created or cloned.

Table 8-1 Layer 2 Tunnel Protocol Interface (IL2TPTunnel)

Attribute Name	Attribute Description	Scheme	Polling Interval
Local and Remote Tunnel Identifications	Local and remote tunnel identifications	Product	Configuration
Local and Remote Tunnel Names	Local and remote tunnel names	Product	Configuration
Remote Address	Remote IP address	Product	Configuration
Control Errors	Control errors count	Product	Configuration
Last Error Code	Last error code value which cause tunnel disconnection	Product	Configuration
Tunnel State	Tunnel state (Unknown, Idle, Connecting, Established, Disconnecting)	Product	Configuration
Sessions Count	Current sessions count	Product	Configuration
Sessions Table	Array of Layer 2 Tunnel Protocol Session Entries	Product	Configuration

Layer 2 Tunnel Protocol Session Entry

The following Layer 2 Tunnel Protocol Session Entry object represents a session within an L2TP Tunnel. It is primarily accessed by the Layer 2 Tunnel Protocol Interface in which it is contained.

Table 8-2 Layer 2 Tunnel Protocol Session Entry (IL2TPSessionEntry)

Attribute Name	Attribute Description	Scheme	Polling Interval
Local and Remote Session Identifications	Local and remote session identifications	Product	Configuration
Subscriber Name	Subscriber name	Product	Configuration
Session Type	Session type (Unknown, LAC, LNS)	Product	Configuration
Session State	Session state (Unknown, Idle, Connecting, Established, Disconnecting)	Product	Configuration
Input and Output Data Counters	Input and output data octets and packets counters	Product	Configuration

Vendor-Specific Inventory and Information Model Objects

Vendor-specific Information Model Objects are implemented only for specific devices of the vendor.

The following sections describe the objects of specific vendors:

•Redback's Layer 2 Tunnel Protocol Peer

•Redback's Layer 2 Tunnel Protocol Group

•Redback's Layer 2 Tunnel Protocol Domain Entry

Redback's Layer 2 Tunnel Protocol Peer

Redback's Layer 2 Tunnel Protocol Peer object describes a logical component, aggregating multiple Layer 2 Tunnel Protocol Interfaces with their configuration, which it is being bound to by its Logical Sons attribute. It is used primarily for managing the creation of L2TP Tunnels.

Table 8-3 Redback's Layer 2 Tunnel Protocol Peer (IL2TPPeer)

Attribute Name	Attribute Description	Scheme	Polling Interval
Local and Peer Addresses	Local and peer IP addresses	Product	Configuration
Local and Peer Names	Local and peer names	Product	Configuration
Tunnel Type	Tunnel type (Unknown, LAC, LNS)	Product	Configuration
Tunnel Mode	Tunnel mode (Null, Static, Dynamic)	Product	Configuration
Maximum and Current Tunnels Counts	Maximum and current tunnel counts	Product	Configuration
Maximum and Current Sessions Counts	Maximum and current session counts	Product	Configuration
Session Authentication Type	Session authentication type (Null, None, Simple, Challenge)	Product	Configuration
Tunnel Password	Tunnel password for the authentication phase of the tunnel establishment	Product	Configuration
RADIUS Identification	Remote Authentication Dial In User Service (RADIUS) identification	Product	Configuration
Hello Time Interval	Time interval in which hello (keep-alive) packets should be sent	Product	Configuration
Control Errors	Control errors count	Product	Configuration
Media Type	Underlying media type (Null, Other, None, UDPLP, Frame Relay, ATM)	Product	Configuration
Group Identification	Object Identification (OID) of layer 2 tunnel protocol group (IL2TPGroup)	Product	Configuration
Domains Table	Array of Layer 2 Tunnel Protocol Domain Entries	Product	Configuration
Logical Sons	Array of aggregated Layer 2 Tunnel Protocol Interface	Product	N/A

Redback's Layer 2 Tunnel Protocol Group

Redback's Layer 2 Tunnel Protocol Group object describes a logical component, load balancing multiple Redback's Layer 2 Tunnel Protocol Peers, which are grouped by its Peer List attribute. It is aggregated by a Traffic Descriptor Container object.

Table 8-4 Redback's Layer 2 Tunnel Protocol Group (IL2TPGroup) 

Attribute Name	Attribute Description	Scheme	Polling Interval
Group Name	Layer 2 tunnel protocol group name	Product	Configuration
Tunnel Algorithm	Tunnel algorithm	Product	Configuration
Dead Time	Dead time	Product	Configuration
RADIUS Identification	Remote Authentication Dial In User Service (RADIUS) identification	Product	Configuration
Peers List	Array of Redback's Layer 2 Tunnel Protocol Peers	Product	Configuration
Domains Table	Array of Layer 2 Tunnel Protocol Domain Entries	Product	Configuration

Redback's Layer 2 Tunnel Protocol Domain Entry

Redback's Layer 2 Tunnel Protocol Domain Entry object describes an Internet Domain, in which members are allowed to open L2TP Sessions within L2TP Tunnels, aggregated by either L2TP Peers or further by L2TP Groups containing this domain. It is aggregated by a Traffic Descriptor Container object.

Table 8-5 Redback's Layer 2 Tunnel Protocol Domain Entry (IL2TPDomainEntry)

Attribute Name	Attribute Description	Scheme	Polling Interval
Domain Name	Layer 2 tunnel protocol domain name	Product	Configuration
Attached To Object	Object Identifier (OID) of either a Redback's Layer 2 Tunnel Protocol Peer or a Redback's Layer 2 Tunnel Protocol Group this domain is attached to	Product	Configuration

Network Topology

Cisco ANA does not support discovery or manual configuration of Layer 2 Tunnelling Protocol (L2TP) Data Link layer topology.

Service Alarms

Table 8-6 lists the L2TP technology alarms.

Table 8-6 LT2P Alarms Summary

Alarm	Severity	Description	Up Alarm
L2TP Peer Is Not Established	Major	The state of a statically configured L2TP tunnel is changed from "established" to anything else. Such a failure may be as the result of a configuration or network problem. The Up alarm is issued when this problem has been fixed.	L2TP Peer is Established
L2TP Peer Was Removed	Info	A dynamically configured L2TP tunnel was removed from a device. This alarm is not issued as a ticket, but it invokes a correlation flow and can be viewed in Cisco ANA EventVision. It also appears in the Cisco ANA NetworkVision application only if correlated to another alarm, such as Link Down or Port Down.	None
L2TP Sessions Count Exceeded	Major	The current percentage of the number of sessions in the L2TP peer has exceeded the maximum configurable threshold. The maximum number of sessions allowed for a single peer is defined by the L2TP peer and L2TP tunnel configuration parameters. The Up alarm when the current percentage of the number of sessions is below the configured threshold.	L2TP Sessions Count Returned to Normal

For detailed information about alarms and correlation, see the Cisco Active Network Abstraction 3.6.5 User Guide.